Process of cracking petroleum oils



June 24, 1930. R. A. HALLORAN ET Al- 1,765,976

l PRocEss oF CRACKING PETROLEUM oILs Original Filed Sept. 4, 1925HEATING ELEMENT composition or tofore been practiced.

Patented June 24, 1930 UNITED STATES PATENT OFFICE RALRH A. HALLORANAND-ARCHIE I.. STROITT, OF BERKELEY, CALIFORNIA, ASSIGN ORS,

BY MESNE ASSIGNMENTS, TO UNIVERSAL'OIL PRODUCTS COMPANY, OF CHICAGO,ILLINOIS, A CORPORATIONOF SOUTH DAKOTA PROCESS or' CRAOKING PETRQLEUMoILs Application led September 4, 1923, Serial No. 660,828. RenewedDecember 5, 1927.`

This invention relates to the art of decracking high-boilingpointpetroleum oils by the application' of heat and pressure for theproduction of relatively low-boiling-point oils.

In nearly alll cracking processes in Which high temperature is employed,development has long been towards the use of relatively small tubes orbanks of tubes for the heating element. In the use of such a heatingeleinent two methods have been employed to raise the oil to thetemperature of the desired cracking reaction: One,--a single or directpassage of the oil through suchheating element in a series flow andthence to a vessel or point where .vaporization takes place, and, theother,-a continuous birculation or cycling of the oil, eitherthermosiphonic or forced circulation, through a closed circuit,including such heating zone or element, to and from a vessel or chamberWhere vaporization takes' place. Cycling with forced circulation, incombination with certain other specified conditions, has here- In 1891pressure .cracking with forced circulation, in combination withcontinuous feed, continuous Withdrawal of residuum,` and continuousdistillation with condensation under atmosphericpressure, was disclosedby Schuchow and Gavrilow in Russian Patent No. 4782 (No. 175 of 1891).Since then various other combinations with forced circulation have beendisclosed in the patent literature.'

In those processes using forced circulation, as employed heretofore,deposition of carbon in the heating element or tubes has seriouslyinterfered With the successful operation of such processes in that ithas limited the length of time during Which the process and apparatuscan be run before shut-down for carbon removal from the heating elementbecomes necessary, and has reduced the heat transfer through the elementto the oil undergoing heating therein, seriously affecting theefficiency of the heatingelement.. and decreasing the heat absorptionrate which must be corrected by increasing the fuel supply to theheating element, thereby rendering control of the operation eX-ceedingly difiicult or impossible and thus affecting not only thechemical reaction butl also the yieldl of the desired low-boilingpointoils.

It has been found that with many of such processes and the apparatusfor'carrying out the same, carbon deposition is a limitation on theyield for any given charging stock beyond which it is not economical tolcarry on the operation. Any provision by which the carbon deposition inthe tubes is reduced prolongs the length of the run for the same yieldand charging rate and for the same length of run produces a higheryield.

It has been customary in the method heretofore utilized in which acyclic process with continuous withdrawal of tarry residuum is employed,to Withdraw such residuum from the same chamber or compartment in whichvaporization takes place and from .which the circulation of the incomingfresh feed starts. As 'a result of this the tarry residuum Withdrawal,instead of being lsubstantially free from loW-boiling-point oils is arepresentative or average sample of the mixture in the vaporizingchamber or compartment and contains, therefore, in addition to the tarryresiduum and fresh stock, unvaporized loW-boiling-point oils. This alsoresults in an undue proportion of the ltarry residuum, resulting aftervaporization has taken place, being circulated through v 'heating,thereby affecting the heat control vof such menstruum and tending tocreate an y undesirable heat differential between the oil as it iscirculated and the oil in the vaporizing chamber; This is forthe reasonthat, if the oil in the vaporizing chamber of the process is to bemaintained at substantially uniform temperature by a circulation of oilfrom said chamber through a heating zone and bak into said chamber, theoil in the heating zone' must be heated to a temperature substantiallyhigher than that of the oil in the chamber to supply the necessary heatof vaporization to the oil in the chamber unless the oil is very rapidlycirculated through the heating zone, so that although the oil passingthrough the heating zone is only heated slightly above that of thevaporizing chamber, such a great volume of oil is circulatedtherethrough that the total additional heat carried thereby to thevaporizing chamber is sulicient to supply the heat demand in thevaporizing chamber. With a relatively large volume of oil undergoingtreatment it -is difficult to maintain this condition without such highrate of circulation as tends to preventl the;

oil in the vaporizing chamber assuming even a substantially quiescentstate and thus any carbon formed therein will be mechanically carriedinto the circulating path and to the heating zone and will not properlysettle out from the chamber where it can be removed.

l In United States Patent No. 11,449,227, granted to Richard W. Hanna onMarch 20, 1923, there is described a cyclic process wherein is employedto material advantage in commercial operation while passing the oilthrough the heating zone or element at intervals of not substantiallymore than ten minutes, a pressure andv temperature in excess of that atwhich thefoil is held at the point at which the 'cycling or circulationeither of said, patents.

begins. Y e

In United States Patent No.-l 1,408,698, dated March 7, 1922, grantedvto Richard W. Hanna, thereis describeda cyclic process in -whichsolvent oil is used to material advantage.

Our invention relates to an improvement 1n the respectlve processes ofsaid Letters s Patent Nos. 1,408,698, and 1,449,227, althrough. ourinvention is not necessarily limited ,to use as an improved processembodying the invention patented or described in We have Adiscoveredthat by maintaining a relatively small volume of the oil undergoingtreatment in the direct path of the circulation and by so conducting theoperation that only the heavyde'rivatives produced by the initialvaporization of the circulating menstruum are in the path ofcirculation, or subject to.being drawn into such circulation, and thereaction is completed in a substantially separate chamber undersubstantially the same conditions of temperature and pressure so thatthe further products formed by the completion of the reaction are notsubject to being drawn into the circulation, a material reduction in thecarbon or coke deposition or formation in the heating tubes is securedand We are able t0 substantially increase the -yield oflow-boiling-pointproducts. Also We effect thereby a saving in fuel. We are also able thusto segregateythe high-boiling-point derivatives of the cracking reactionor tarry residuum from the, menstruum being cycled and withdraw the samesubstantially without any effect from these heavy derivatives or tarryresiduum upon the circulating menstruum. e Y

Our invention will be best understood by reference to the accompanyingdrawings, which are used merely to illustrate a preferred embodiment ofour invention ,and which, it is understood, may be widely varied Withoutdeparting from the spirit of the invention, and in which Figure 1 is adiagrammatic View of an apparatus by which my invention may bepracticed.

Fig. 2 is an enlarged cross-sectioned View of the evaporator, showingmore in detail the Vcycling or initial vaporizing chamber andthe-separate final vaporizingl chamber.

In the drawing, 1 indicates a storage vessel for thehigh-boiling-pointoil which is to be cracked; l2 is a suitable pump designed to pump suchoil from the storage, l, and forcethe same through pipe or conduit 3. 4indicates a storage vessel for a solvent oil which is tio be mixed withthe high-boilingpoint oil to be cracked for the purpose of taking intosolution' the heavy bodies produced by cracking such high-boiling-pointthe preferred form and embodiment of my process. 5 indicates a pump toforce solvent oil through line 6finto line 3, where'it is i mixed withthe oil to be crackedv Itis obvious, however, that the mixing of the oilto be`fcracked and the solvent oil may take 4place before the same aresupplied to the The use of such solvent oil is incident, however, onlyto through a waste heat exchanger 7, and' thencethrough a continuationof such pipe or conduit 3, into a reflux condenser 8, where suchcharging stock is subjected to the waste heat of the reflux condenservand where it joins with the reflux and flows `through pipe 9 into thevaporizing chamber 10 of the druml 11. .The heating coil or element 19of the cracking system is preferably mounted in a suitable furnace 18,which may be heated in any preferred manner; indicates a pump whichtakes suction on the'vaporizing chamber 10 through pipe 16, and causes astream of the liquid therefrom to be circulated through pipe 17, heatingcoil 19, and pipe 20, back to the vaporizing chamber 10. 21 indicates asuitable valve, by means of which a differential pressure may bemaintained on the oil in the vaporizing chamber 10,. and the heatingcoil 19. 13 represents a Abail-le extending across vthe drum 11,A

and so located that the vaporizing chamber 10, is relatively small ascompared with the compartment 12. This baffle completely closes ofl" thevaporizing chamber 10, from the compartment 12,'except for a smallopening about six inches in diameter next to the lowest point ontheperiphery of the drum 11 14 represents a bank of tubes arranged in ahorizontal plane and extending through the l baffle 13. These tubes areclosed on the end located in compartment 12. .The other end is open andis upturned, so as to extend above the level of the liquid kept in thevaporizing chamber 10. Within the final reaction and vaporizing chamber12 .the

4.bottoms of these tubes 14 are provided with suitably spaced smallopenings through which the vapor, evolved in the initial vaporizing andcycling chamber 10, is forced to flow into the body of reacting oil inthe chamber 12. These tubes'14 are to be' tightly welded to the bathe-13to insure the forcing of the passage of all such vapor Ifrom chamber 10through tubes 14 into chamber 12. Themaximum level of oilin the chamber(10 is determined by the level of the discharge openings from4 the tubes14 into the chamber 12. The level of reacting oil in the chamber 12 isregulated by the withdrawal of residual oil therefrom and the maximumlevel of oil in chamber 10 is not dependent upon the level of oil inchamber 12., Baffles 22 are for the purpose of breaking up convection oreddy currents in compartment 12. s

A' vapor line 23, extends from compartment 12 tothe reflux condenser orcolumn 8,

and thence through heat exchanger 7 to condenser 24. The condensateflows into a receiving'drum 25, Where the fixed or uncondensable gasesare` released through conduit 28 and valve 29. The condensate isreleased through valve 26 and passes to storage 27.

31 represents a 'discharge pipe through which tarry residuum iswithdrawn continuously from the system and passed through the cooler 32to storage 33. The withdrawal of this tarry residuum is controlled byvalve 3.0. f

With such an'organized apparatus or system as thus illustrated anddescribed, we

'the cracking operation desired. 'When my process is performed in such asystem, we preferably maintain in the final evaporating chamber arelatively large volume of the v re-acting oil undergoing vaporizatlon.Preferably we conduct the vapors from the cycling chamber 10 into thefinal evaporating chamber in such manner as to discharge them into thisbody of oil as, for instance, by means vof the vapor conduit pipes 14..By thus discharging these hot vapors into vand causing them to risethroughk this body of re-act-ing oil vaporization-thereofis assisted andan economy of the heat demand effected. Thus a further reduction in thepotential formation of carbony or heavy derivatives in the heatingelement. is secured and an increased' yield for the same charging rateis thus secured. The final withdrawal of the low-boiling-point vapors isfrom this final evaporating chamber12. The withdrawal ofthe heavyderivatives of the cracking operation is also 'from such chamber 12 andpreferably as far removed as possible from the actual cycling menstruumof the systeml The reacting oil is maintained for an appreciable time inthis chamber 12 and the main precipitation or settling out of thecarbon, tarry bodies or heavy derivatives orl cracking takes placetherein. The period vof re-action is thus prolonged by the reaction ofthe oil in the final evaporatinfr chamber 12, as described, withoutpermittingV this prolonged reaction, and the consequent precipitationand settling out of the oil of the heaviest derivatives, to effect theoperation of the cyclic system, which includes, as before described, aheating zone or coil and a -cycling chamber, in which latter materialvaporization is effected.l

However, our invention is not necessarily limited to conducting thevapors from the cycling or initial vaporizing chamber into the re-actinoil in the final vaporizing chamber. I desired such vapors may bepermitted to flow from the cycling chamber over into the vaporizingspace above the reacting oil in the final chamber 12, as by providing asuitable opening (not shown) at or near the" top ofthe baffle 13, ortheymay be separately discharged, as through a Itwill be apparent in thepractice of this process that a very considerable amount of vaporizationwill take place in the Vaporizing chamber 10. The vapors here formedinclude the lighter or desirable fractions, and, in addition, a largeproportion of heavier products, which will later be returned to thesystem as reflux from the tower 8, all kof which vapors mustof necessitypass through the tubes 14 and into the oil in compartment 12 of thesystem.

It will further be apparent that the oil passing from compartment 10through the opening in the baille 13 into theicompartment 12 will beheldat a cracking temperature. This oil is withdrawn at the .chamber 10 fromthe circulating menstruum of the system. The rate of withdrawal isdetermined by the rate of withdrawal of the heavy derivatives ofcracking from the chamber 12 plus the rate of withdrawal of vapor formedin the chamber 12, from the chamber 12, less all condensation in thechamber 12 of vapor entering thereinto through the conduits 14. y v,

There will be a sli4 ht fall in temperature due to small radiationlosses and toheat absorbed by additional vaporization andl reaction inthis compartmente12f Itis this additional reaction and vaporizationwhich so greatly adds to' the increase in yield of the process and makesit possiblel to withdraw a residuum substantially free from constituentsdesired as distillates. The construction of drum 11 is butdiagrammatically indicated, it being understood that in practice thedrum must of course be supported upon a suitable foundation and inaccordance with ordinary refinery practice would be suitably insulatedagainst dissipation of heat by radiation or convection.

Very satisfactory results have been obtained by the use of this processincluding the use of baffle 13 but without the use of the tubes 14 inwhich case a vapor opening is arranged at the top ofbaiile 13 as beforereferred to. It has been found, however, that the fall of temperature inlthe oil in compartment 12 is greater and the increase in yield lessthan with the use of the vapor tubes 14. f

While we have shown in the drawings the cycling and initial vaporizingchamber 1.0 and the final reacting and vaporizing chamber 12 as parts ofa single element,'

indicated in the drawing as. an'fvaporator, it is obvious that thefunctions and mode ol operation of these would not be 'changed nor wouldthe process be materially altered if the initial vaporizing and cyclingchamber 10 and the final reaction and vaporizing chamber 12 wereconstructed as totally independent units and merely so connected as to`have the described functions and funcrocess and system as a whole. We,thereore, wishit understood that in so far as the drawings illustrate orwe have herein described these two chambers as parts of a singleelement, such has been done conventionally and lfor convenience and wedo not thereby limit our invention thereto.

` Preferably condensation of the vapors in the condenser 24 is underpressure maintained on the system by regulation of the valve 26. Thecrackingoperation may be performed at any required temperature and undersuch pressure above atmospheric as may be best suited to the particularcon- -ditions and oils to be treated.

In the preferred embodiment as stated above, the reflux is joined withthe feed and is introduced into and becomes a part of the circulatingmenstruum. The menstruum is thus maintained substantially free fromheavy and tarry-bodies and the diculties resulting from carbondeposition substan` tially reduced. Itis apparent, however,

that the feed and reflux may be introduced into other parts than thoseindicated.

We claim Y 1. The cycli'jj'rocessofi-Cracking petroleum oils under'`'a5'"substfintiall ,v constant temperature andpres'sure, both-'o A whichare substantially unifol'mthroughout the crack-f ing system,.. whichincludes forcibly'circulat-g ing the oilf'iindergoing treatmentin arelatlvely small stream from an initial vaporizing and cycling chamberthrough a heatf ing zone and back into said chamber, passing a portionof the oil in circulation from said cycling chamber to a non-cyclingchamber, in .such manner as to maintain iny said cycling chamber arelatively small volume of oil and in said non-cycling chamber arelatively vlarge volume of said oil in order that heavy derivatives areformed mainly in said non-cycling chamber, effecting thgcompletion ofthe desired cracking reaction 1n said non-cycling chamber, withdrawingthe vapors, and withdrawing residual oil.

2. The cyclic process of cracklng petroleum oils under constanttemperature and pressure, both of which are substantially `uniformthroughout the cracking system,

which includes forcibly circulating the oil undergoing treatment in arelatively small stream from an initial vaporizing and -cy-l clingchamber through a heating zoneand back into said chamber, feeding theoil to be treated to said circulation in suficient quantity to maintaina substantially uniform volume of oil in circulation, withdrawing aportion of the partially converted oil from the circulL'iing menstruumat said cycling chamber and passing it to a second reacting andvaporizing chamber, maintaining such oil in said second chamber for atime suflicient to permit the comple.- tion of the desired reaction andunder the required conditions of ressure and temperature without recircation, withdrawing the vapor, and withdrawing residual oil.

3. The cyclic process of cracking petroleum oils under constanttemperature and pressure, both of which are substantially uniformthroughout the cracking system, which includes forcibly circulating theoil undergoing treatment in a relatively small stream from an initialvaporizing andcycling chamber throu h a heating zone and back into saidchamber, feeding the oil to be treated to said circulation in asufficient quantity to maintain a substantially uniform volume of oil incirculation, withdrawing aportion of the partially converted oil fromthe circulating menstruum-l at Said chamber and passing it to a secondreacting and vaporizing chamber, maintaining liquid communicationbetween said chambers, maintaining a closed condition against thewithdrawal of vapor from said cycling chamber except through the secondchamber kand through the reacting oil therein, withdrawing the vaporfromsaid second chamber, and withdrawing residual oil from said secondchamber.

4. A process ofv cracking petroleum oils under a substantially constanttemperature and pressure, both of which are substantially uniformthroughout the cracking system, which includes first forciblycirculating the oil undergoing treatment from a vaporization and cyclingchamber through a heating zone and back into said chamber, continuallywithdrawing a portion of the oil from such circulating system andpassing it to a cracking chamber in which a relatively larger volume ofoil is maintained than in said vaporization and cycling chamber, the oilin said second chamber being maintained in a quiescent state to permitremoval of residuals, the vapor lformed in the first chamber beingpassed through the oil in the second chamber', feeding the oil tobe'treated to said circulation in suicient quantity tomaintainsubstantially a uniform volume of oil in circulation,withdrawing the vapors formed, and withdrawing residual oil from saidsecond chamber so as to remove heavy derivatives therefrom. l 5.' Acyclic process of cracking petroleum oils which 'includes heating theoils undergoing cracking by circulating the oils from an evaporatinglchamber to and through a chamber to said second chamber, and withldrawing the vapors.

6. In the pressure distillation -of oils heavier than gasoline '.for theproduction of gasoline-like products, maintaining a plu-y body tomaintain all said oil bodies at cracking temperature, the later oilbodies deriving heat solely from said oil passed through the heatingzone.

7. In the pressure distillation of oils heavier than gasoline for theproduction of gasoline-like products, maintaining a` plurality of bodiesof oil and causing oil to flow successively therethrough, withdrawingoil from the first of said oil bodies, passing it together with freshoil through a heating Zone and returning such oil in heated state tosaid first oil body to maintain all said oil bodies at crackingtemperature, the later oil bodies deriving heat solely from said oilpassed through the heating zone.

8. In the pressure distillation of oils heavier than gasoline for theproduction of gasoline-'like products, maintaining a plurality of bodiesof oil and causing oil to flow successively therethrough, said oilbodies being at conversion temperatures, removing vapors therefrom,cooling said vapors to condense therefrom products heavier than thedesired gasoline-like products, withdrawy ing zone and returning .suchoil in heated lstate to said first oil body to maintain all said oilbodies at cracking temperature, the later oil bodies deriving heatsolely from said oil passed through the heating zone.

Signed at Richmond, California, this 28th day of August, 1923.

4 RALPH A. HALLORAN.

ARCI-IIE L. STROUT.

heating zone and back into the evaporating chamber, passing a portion ofthe heated oil to a second chamber in which the cracln'ng reaction iscontinued while maintaining the 'goil quiescent and withdrawing residualoil

